1. Field of the Invention
The present invention relates to an apparatus and method for preventing sand from settling in wellbores. More specifically, the invention relates to using recirculated fluid to prevent sand from settling in lateral wellbore lines.
2. Description of the Related Art
Some oil-bearing geologic formations have a high sand content. One such example is the “oil sands” field in Canada. Minerals such as oil are located within the sand. To produce the minerals, wellbores are drilled into the sand formation and lined with casing. The wellbores are frequently lateral, or horizontal, wellbores through the sand.
To produce the minerals, water is injected into the sand formation. The minerals and water move into the wellbore through perforations in the casing. An electrical submersible pump (“ESP”) is suspended from tubing in the wellbore. The ESP is submerged in the wellbore fluid which, in this case, may contain water, oil, and sand. The wellbore fluid enters the pump inlet and is pumped out through the tubing from which the ESP is suspended.
Sand is suspended in the fluids that move into the wellbore. As the fluids move through the wellbore, some of the sand settles out of suspension and forms a packed layer of settled sand in the wellbore. Over time, the wellbore may become so occluded with settled sand that the flow rate through the wellbore is severely reduced. Some lateral wellbores that typically flow more than 3000 barrels of fluid per day (“bfpd”) can drop to 700-400 bfpd due to restrictions in the wellbore caused by settled sand. The settled sand must be cleaned out when production drops too low.
To remove the sand, a cleaning tool must be run through the lateral wellbore. The cleaning tool could be a coil that rotates through the wellbore to scarify the sand. The disadvantage of cleaning tools is that they require the ESP to be withdrawn from the wellbore to make room to insert the cleaning tool. Production time is lost during the removal of the ESP, the cleanout process, and the subsequent reinsertion of the ESP. It is desirable to prevent sand from settling in the wellbore during production or be able to clean out the sand without having to withdraw the ESP.